1. Field
The presently disclosed subject matter relates to wavelength converting devices, methods for manufacturing the wavelength converting devices and lighting units using the wavelength converting devices. More particularly, the presently disclosed subject matter relates to the wavelength converting devices that can provide favorable light distribution patterns having various colure lights including a substantially white color light by scanning a laser beam, the methods for efficiently manufacturing such the devices with high accuracy, and relates to the lighting units using such the devices that can also emit a large amount of light intensity having a high light-efficiency, and which can emit the various color lights having a high color uniformity in order to be able to use for a stage light, a street light, a projector, a vehicle light, a spot light, etc.
2. Description of the Related Art
Semiconductor light-emitting devices, in which a part of light emitted from a semiconductor light-emitting chip is converted into light having a different wavelength by a wavelength converting layer and in which a mixture light including the light having the different wavelength mixed with the light emitted directly from the light-emitting chip is emitted, have been used as a light source for various lighting units such as a vehicle headlight. When the semiconductor light-emitting devices is used as a light source for a headlight, the semiconductor light-emitting devices may locate each of the semiconductor light-emitting chip and the wavelength converting layer at a different position and may emit a substantially white light toward a road in accordance with a design and the like of the headlight.
A conventional headlight having such a structure is disclosed in Patent document No. 1 (Japanese Patent Application Laid Open JP2009-266437). FIG. 8a is a schematic cross-sectional view depicting the conventional headlight disclosed in Patent document No. 1. The conventional headlight 90 includes: a first casing 95; a second casing 96; a semiconductor light-emitting chip 92 located underneath the first casing 95 so as to emit light in downward direction of the first casing 95; a wavelength converting layer 91a including a filter 91b to select a wavelength, formed in a planar shape, and attached to the first casing 95; and a first reflector 93 located underneath the first casing 95, facing the semiconductor light-emitting chip 92 and the filter 91b included underneath the wavelength converting layer 91a, and the light emitted from the semiconductor light-emitting chip 92 passing though the wavelength converting layer 91a via the filter 91b after reflecting the light with the first reflector 93, and thereby the light changing to a mixture light having a substantially white color tone, which includes a part of the light emitted directly from the semiconductor light-emitting chip 92 mixed with a wavelength-converted light having a different wavelength from another of the light.
In addition, the conventional headlight 90 also includes: a second reflector 94 attached on the first casing 95 so as to be located in an opposite direction of the first reflector 93 with respect to the wavelength converting layer 91a, and thereby the mixture light, which is emitted from the wavelength converting layer 91a after the reflective light from the first reflector 93 passes from the filer 91b across the wavelength converting layer 91a, reflecting in an opposite direction of the semiconductor light-emitting chip 92 and in a direction toward the second casing 96; and a projector lens 97 attached to the second casing 96, and the mixture light being emitted from the projector lens 97 in a frontward direction of the headlight 90.
When the semiconductor light-emitting chip 92 is a blue light-emitting diode (LED) emitting blue light and when the wavelength converting layer 91a is a yellow phosphor such as yttrium aluminum garnet (YAG), the conventional headlight 90 may emit the mixture light having a substantially white color tone due to an additive color mixture of a part of the blue light emitted from the blue LED and yellow light excited by the yellow phosphor using another part of the blue light as an exciting light. More specifically, a method for emitting the mixture light having the substantially white color tone in the conventional headlight 90 will now be described with reference to FIG. 8b, which is an explanatory view to explain the method for emitting the mixture light having the substantially white color tone in the conventional headlight 90.
The FIG. 8b revises a relation between the semiconductor light-emitting chip 92 and the wavelength converting layer 91a as a linear structure without the first reflector 93 to facilitate an understanding of the method in Patent document No. 1. In blue light 98B emitted from the semiconductor light-emitting chip 92, the substantially whole blue light 98B may enter into the wavelength converting layer 91a via the filter 91b, and may vary a mixture light 99M having the substantially white color tone due to an additive color mixture of the part of the blue light 98B and yellow light 98Y excited by the wavelength converting layer 91a including the yellow phosphor using another part of the blue light 98B as the exciting light.
In this case, a partial light 98BY of the blue light 98B may reflect from the wavelength converting layer 91a toward the filter 91b. Hence, the light 98BY may return into the wavelength converting layer 91a by reflecting the light 98BY using the filter 91b, and thereby the conventional headlight 90 may improve a light-emitting efficiency thereof. However, because the light 98BY may reflect on a bottom surface of the wavelength converting layer 91a and also reflect on a top surface of the filer 91b, the light 98BY may become multipath reflection light.
Accordingly, the mixture light emitted from the top surface of the wavelength converting layer 91a may become white color light having yellow-tinged light on peripheral region of the wavelength converting layer 91a. When the white color light having yellow-tinged light on peripheral region of the wavelength converting layer 91a is enlarged and projected from the projector lens 97 via the second reflector 94, the conventional headlight 90 may project the white color light having a color variation such as a yellow ring toward a road, although the conventional headlight 90 may improve the light-emitting efficiency thereof. Therefore, the conventional headlight 90 may not necessarily provide a favorable light distribution for drivers of subject vehicles, oncoming vehicles, etc.
A conventional semiconductor light-emitting apparatus, which may prevent the above-described color variation, is disclosed in Patent document No. 2 (Japanese Patent Application Laid Open JP2013-102078), which is owned by Applicant of this disclosed subject matter. FIG. 9 is a schematic explanatory perspective view showing the conventional semiconductor light-emitting apparatus disclosed in Patent document No. 2. The conventional semiconductor light-emitting apparatus 80 includes: a semiconductor light source 85 having a light beam diameter 85D, and a wavelength converting plate 82 including a plurality of wavelength converting chips 87 and a plurality of plates 86, which divides the wavelength converting plate 82 into the plurality of wavelength converting chips 87.
In the conventional semiconductor light-emitting apparatus 80, a diameter 85D of the light beam emitted from the semiconductor light source 85 becomes smaller than each of widths in directions of X-direction and Y-direction of each of the wavelength converting chips 87 so that the light beam emitted from the semiconductor light source 85 can enter into each of incident surfaces of the wavelength converting chips 87. Additionally, the plurality of plates 86 are made from a metallic plate having a high reflectivity such as a silver, aluminum and the like so that the light beam entering into each of the incident surfaces of the wavelength converting chips 87 may be emitted from a respective one of light-emitting surfaces of the wavelength converting chips 87. Thereby, the conventional semiconductor light-emitting apparatus 80 may prevent the above-described color variation such as the yellow ring.
Recently, vehicle headlights using a semiconductor light source and a mirror that can provide various light distribution patterns for drivers and headlight systems using the headlights that can vary a light distribution pattern so that the drivers can drive a motor vehicle safely in accordance with surroundings such as an oncoming vehicle, a forward travelling vehicle, a road and the like have been developed. Such a headlight system is disclosed, for example, in Patent document No. 3, which is owned by Applicant of this disclosed subject matter.
When the vehicle headlights use a semiconductor light source and a mirror to provide various light distribution patterns for the drivers, light emitted from the semiconductor light source may scan on the wavelength converting plate 82 including the plurality of wavelength converting chips 87. In this case, a part of the light emitted from the semiconductor light source hits on the plurality of plate 86 and may return toward the semiconductor light source. Accordingly, when the vehicle headlights having such a structure, in which the light scans on the wavelength converting plate 82, use the wavelength converting plate 82 including the plurality of wavelength converting chips 87, the vehicle headlights may decrease a light-emitting efficiency thereof.
The above-referenced Patent Documents and an additional document are listed below, and are hereby incorporated with their English abstracts in their entireties.
1. Patent document No. 1: Japanese Patent Application Laid Open JP2009-266437
2. Patent document No. 2: Japanese Patent Application Laid Open JP2013-102078
3. Patent document No. 3: U.S. Pat. No. 8,956,025
4. Patent document No. 4: U.S. patent application Ser. No. 14/583,587
The disclosed subject matter has been devised to consider the above and other problems, characteristics and features. Thus, embodiments of the disclosed subject matter can include various wavelength converting devices, which can provide various desirable light distribution patterns by scanning a laser beam using a movable mirror. In this case, the wavelength converting devices can emit various color lights including a substantially white color light having a high light-efficiency and high color uniformity. In addition, the embodiments of the disclosed subject matter can include methods for efficiently manufacturing such the wavelength converting devices with high accuracy, and also can include lighting units using the wavelength converting devices that can also emit a large amount of light intensity having a high light-efficiency, and which can emit the various color lights having a high color uniformity.